The goal of this exploratory proposal is to discover genes whose expression defines the specialization of vasomotor sympathetic neurons. Such genes represent new tools for manipulating sympathetic neurons and blood pressure control in experimental studies and for developing new therapeutic strategies. The approach will exploit a transgenic reporter mouse in which NPY-promoter sequences drive expression of green fluorescent protein. Messenger RNA will be purified from manually sorted identified neurons, then amplified and analyzed with microarrays to detect gene expression. The proposal is predicated on the novel concept that half of the entire sympathetic outflow of spike activity originates in the ganglia, not the central nervous system, and upon the hypothesis that synaptic amplification in functional subsets of vasomotor sympathetic neurons is tuned to the needs of different vascular beds. Experiments will address one specific aim, which is to discover genes that distinguish vasomotor from non-vasomotor neurons and that identify subsets of sympathetic neurons controlling different aspects of cardiovascular function. Gene expression will be analyzed in four different ganglia that control brain circulation, the heart, the kidney and limb muscle vasculature. The expression analysis will be further refined by using a retrograde tracer to back label neurons that control circulation in muscles, the skin and the kidney and through analysis of gene expression in single cells. Validation studies will employ quantitative PCR, immunocytochemistry and electrophysiology. This project has potential for high-impact. Strong evidence now indicates that hyperactivity in vasomotor postganglionic sympathetic neurons presages 50% of human hypertension and further contributes to problems associated with heart failure and renal failure. These conditions impose a tremendous public health burden, yet existing therapies for clinical management of hypertension remain inadequate. Finding tools for selectively manipulating postganglionic sympathetic activity in cell types that regulate specific vascular beds will advance fundamental scientific and medical understanding of integrated autonomic physiology.